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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 104 |
| 6 | 572 |
| 7 | 3688 |
| 8 | 27200 |
| 9 | 208108 |
| 10 | 1782304 |
| 11 | 17035000 |
| 12 | 176048408 |
| 13 | 1966114726 |
| 14 | 23376757520 |
| 15 | 302105991330 |
| 16 | 4109445417380 |
[1,2,6,24,104,572,3688,27200,208108,1782304, 17035000,176048408,1966114726,23376757520, 302105991330,4109445417380] |